Amplifying apparatus



July 21, 1925.

F. R. ELDER AMPLIFYING APPARATUS Filed Sept. 27, 1924 l w/enter: FrankR.E.lde'r-',

9 M His Attornev cathode and plate.

Patented July 21, '1925.

UNITED STATES 1,547,152 PATENT OFFICE.

FRANK R. ELDER, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

AMPLIFYING ArrARA'rus.

Application filed September 27, 1924. Serial No. 740,894.

To all whom it may concern:

Be it known that I, FRANK R. EnDER, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certaln new and useful Improvements in Ampl fyingApparatus, of which the following is a specification.

My present invention relates to electron discharge apparatus andcircults for amplifying anddetecting high frequency signaling currents.One of the ob ects of my invention is to provide a circuit arrangementwhereby the amount of amplification WllICll may be obtained with asingle device may be greatly increased.

It has been proposed in the past to em ploy a three-electrode electrondischarge device for the simultaneous amplificatlon of radio frequencycurrents and audio frequency currents. Another object of my 1nvention isto provide a practical system whereby a four-electrode electrondischarge device, particularly one of the negative resistance ofpliodynatron type, may be employed for the simultaneous amplification ofboth radio and audio frequency currents.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My invention,itself, however, both as to ts organization and method of operatlon Wlllbest be understood by reference to the following description taken inconnection with the accompanying drawing in which Flg 1 showsdiagrammatically one form of my 1nvention, and Fig. 2 shows amodification thereof.

I have indicated in the drawing an electron discharge device 1 havingthe usual electron emitting cathode 2, plate electrode 3, and two grids4 and 5 interposed between The grid 4 serves as a control grid and thegrid 5 serves as an anode for receiving impact electrons emitted fromthe plate 3. A source of potential6, which is connected in the circuitsbetween the cathode 2 and plate 3 and grid 5 furnishes suitable valuesof potential for application to electrodes 3 and 5 to produce a negativeresistance in the plate circuit by reason of the emission of impactelectrons from the plate 3. The potential applied to the plate 3 may beadjusted by means of the sliding contact on resistance 7, which isconnected in shunt to source 6. By suitable adjustments the negativeresistance produced in this Way may be made great enough to compensatefor the losses of the system, and at the same time cause the productionof oscillations, if desired.

In the system shown in Fig. 1, the plate circuit may be tuned by meansof inductance 8 and variable condenser 9 to the frequency of the highfrequency oscillations to be amplified in case modulated waves are to bereceived, or to a slightly different frequency if unmodulated waves areto be received. By suitable adjustment this amplification of the highfrequency currents may be made asymmetric so that the resulting currentin the plate circuit will be capable of operating a signal indicator.The low frequency component of the current thus produced in the platecircuit is fed through the primary 10 of a transformer, the secondary 11of which is included in a link circuit with the primary 12 of a secondtransformer having a secondary 13 included in the input circuitconnected between cathode 2 and'control grid 4.

I have indicated the application of my invention to the amplificationand detection of high frequency slgnaling currents received upon anantenna 14 and supplied by a coupling transformer 15 to the tuned inputcircuit 16 of device 1. Received radio frequency currents are amplifiedby device 1, and the audio frequency currents produced in the .platecircuit are supplied by transformers 1011, 12-43, to the input circuitand also amplified. An indication of the amplified audio frequencycurrents may be obtained in the usual telephone receiver 17 connected inthe circuit of grid electrode 5. By-pass condensers 18, 19, 21 and 22are preferably provided for by-passing around the transformer-windings10 and 13 and resistance 7, the radio frequency components of thecurrents flowing in the plate circuit and the input circuit.

In the operation of the system described, the adjustment should be suchthat the damping of the high frequency oscillating circuit is low andthe damping of the low frequency circuit is high; in other words, thetransformer in the plate circuit should be incapable of causing audiofrequency oscillations by reason of its inductance and distributedcapacity. A resistance 20 inserted in the link circuit between the platecircuit and the input circuit will increase the damping and thus preventoscillations.

In the arrangement shown in Fig. 2, the link circuit is omitted, thesecondary 11 being connected directly in the input circuit. In thiscase, the tendency of the plate circuit to oscillate at the audiofrequency may be prevented by a series resistance 23 in the platecircuit.

While I have shown and described only two modifications of my invention,it will be apparent that many modifications in the particular apparatusemployed and 1n the manner in which it is connected inthe circuit may bemade without departing from the scope of my invention as set forth inthe ap ended claims.

Vhat I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. The combination in an amplifying system of an electrondischarge device having an electron emitting cathode, a plate electrodeand two grid electrodes interposed between cathode and plate, circuitconnections between the cathode and each of the other electrodes, meansfor impressing high frequency currents to be amplified upon the circuitbetween the cathode and one of said grids, sources of potentialconnected in the circuits between the cathode and the plate and secondgrid of such value that a negative resistance is produced in the platecircuit of high enough value to compensate for the losses of the system,means for tuning the plate circuit to a desired high frequency, meansfor producing low frequency currents in the plate circuit and supplyingthem to the first grid circuit, and means for producing an indication ofthe amplified low frequency currents in the circuit of the second grid.

2. The combination in an amplifying sys' tem of an electron dischargedevice having an electron emitting cathode, a plate electrode and twogrid electrodes interposed between cathode and plate,circuit-connections between the cathode and each of the otherelectrodes, means for impressing high frequency currents to be amplifiedupon the circuit between the cathode and one of said grids, sources ofpotential connected in the circuits between the cathode and the plateand second grid of such value that a negative resistance is produced inthe plate circuit of high enough value to compensate for the losses ofthe system, means for tuning the plate circuit to a desired highfrequency, a link circuit containing a resistance and which forms acoupling between the plate circuit and the circuit of the first grid,and means for indicating the resultant currents produced in the circuitof the second grid.

The combination in an amplifying system of an electron discharge devicehaving an electron emitting cathode, a plate electrode and two gridelectrodes interposed between cathode and plate, circuit connectionsbetween. the cathode and each of the other electrodes, means forimpressing high frequency currents to be amplified upon the circuitbetween the cathode and one of said grids,,sources of potentialconnected in the circuits between the cathode and the plate and secondgrid of such value that a negative resistance is produced in the platecircuit of high enough value to compensate for the losses of the system,means for tuning the plate circuit to a desired high frequency, meansfor producing low frequency currents in the plate circuit, means forpreventing audio frequency oscillations in the plate circuit, a couplingbetween the plate circuit and the circuit of the first grid, and meansfor indicating the resultant currents produced in the circuit of thesecond grid.

In witness whereof, I have hereunto set my hand this 26th day ofSeptember, 1924.

FRANK R. ELDER.

